This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Over the past two decades, considerable strides have been made in the prevention of mother-to-child transmission (PMTCT) of HIV. The administration during pregnancy of virologically suppressive antiretroviral drug combinations conventionally referred to as highly-active anti retroviral therapies (HAART), cesarean section delivery, and infant formula-feeding (FF) have led to a decrease of the risk of MTCT to less than 2% and the virtual elimination of new pediatric HIV infection in the U.S., Europe, and other resource-advantaged settings. Remaining issues essentially revolve around improved service delivery, in particular the detection of all HIV-infected women prior to conception and early enough during pregnancy so that appropriate counseling and appropriate ART can be provided. Determining the safety of stopping HAART when used solely for prophylaxis of MTCT remains an important unresolved issue.